The invention relates to rf receivers and more particularly to a channelized receiver for determining the frequency of a received rf signal.
A frequent problem encountered in high sensitivity, narrow band radar intercept receivers is to tune them to receive a signal having an unknown frequency. Reducing the bandwidth of a receiver generally increases its sensitivity, but results in tuning difficulties because the narrow bandwidth must be more precisely centered with respect to the incoming signal. One way conventional radar intercept receiving systems have tried to eliminate this problem is to search for the unknown signal with a less sensitive wide band receiver, and, once having detected a signal, tune a narrow band receiver to the detected signal. As the signal-to-noise ratio of the unknown signal becomes lower, the more difficult it is to utilize this method. In addition, it is usually desirable to rapidly identify the unknown signal in order to quickly tune the narrow band receiver to that frequency. Accordingly, channelized receivers having a plurality of filters each defining a contiguous passband portion of a search bandwidth have been utilized to quickly identify a channel in which an unknown signal lies, this channel then being used to identify a tuning frequency for a narrow band receiver. However, as the dynamic range of an unknown input signal increases, it becomes more difficult to determine the frequency of the signal without the use of complicated and complex redundancy comparison circuitry which is required when strong input signals provide output signals of substantially equal magnitude at two or more of the channelizer filters.